Ammonium zinc chloride (AZC) crystals doped with Mn2+ in different concentrations were grown from aqueous solutions at constant temperature. The dielectric constant (ε), dielectric loss (tan δ) and the ac conductivity (σac) along the polar axis were measured as functions of temperature and frequency. The temperature range covered the four high-temperature phases and the measuring frequency extended between 1-100 kHz. The measured properties facilitated the discussion of a model describing formation, annihilation and pinning of the discommensuration in crystal lattice and/or by structural imperfections. The effect of AZC decomposition in the normal phase and the possibility of protonic evolution on the ac conductivity were also considered. The presence of Mn2+ in the position of Zn2+ affected considerably the anomalies detected around the phase transition temperatures of ε, tan δ and σac. Conduction by translation and/or reorientation hopping are possible in two different frequency ranges depending on the crystal phase character.

*On leave of absence from Physics Department, Faculty of Science, Assiut University, 71516 Assiut, Egypt